In remodelling of older offices, a frequent improvement is the addition of an acoustical tile ceiling or "drop ceiling." Such acoustical tile ceilings typically involve a grid or framework which is hung from the existing ceiling, and into which are placed acoustical ceiling tiles.
The grid or framework is typically hung from the existing ceiling using a toggle bolt of the type illustrated as toggle bolt 100 in FIG. 1. Toggle fastener 100 typically consists of a bolt 102 onto which is mounted a nut 104 and a washer 106, and a spring-loaded wing toggle 108. The correct method of installing such toggle bolts 100 is to drill a hole in the existing ceiling and to insert the fastener 100 into the hole, causing toggle wings 110 to be compressed against the bolt 102, until the wing toggle 108 exits the other side of the existing ceiling, whereupon the wings 110 expand preventing the toggle fastener 100 from being pulled back through the hole.
It is to be appreciated that prior to insertion of the toggle bolt 100 into the hole, that it is often necessary to back the nut 104 away from the toggle 108 to provide clearance for the wings 110 to be folded back in order to insert the toggle through the hole. This can add significantly to the time needed to install the toggle.
After the toggle wings 110 are opened, in the correct method of installation, the nut 104 and washer 106 are advanced until tight against the ceiling. It is typically a fire code requirement that such washers 106 be advanced until flush against the ceiling to block the open channel, formed by making the ceiling hole, into the open plenum above the existing ceiling, to minimize risk of a fire spreading upwardly through a building. In addition, it is desirable to tighten the nut and washer to insure that the toggle bolt 100 is tightly secured to the ceiling.
The new acoustical ceiling grid is then hung by a wire element passed through the opening 112 in the end of bolt 102 and which is twisted around the gridwork.
While the method using the prior art toggle fastener 100 is effective to hang an acoustical ceiling gridwork, it is time consuming. In particular, the steps of backing the nut 104 away from the toggle 108 and then advancing the nut 104 to correctly install the washer as an effective firestop require significant amounts of time, especially when it is considered that building code requirements typically require use of at least 16 such fasteners per each 10 foot by 10 foot square area of ceiling, such that hundreds of such fasteners will be required for a commercial construction project. It is to be appreciated that the thickness of the existing ceiling may be greater than expected and significant time may be spent in backing off and adavancing the nut.
A potentially dangerous problem also arises with the method of installing acoustical ceilings using such prior art fasteners 100. In particular, to save time (and cost), installers frequently do not completely tighten the nut 104 and washer 106 against the drywall ceiling panel, thereby leaving an open passageway between the two sides of the existing ceiling, which as noted above, is a fire code violation. An incomplete firestop also can arise if the mounted toggle bolt is not properly centered in the hole in the ceiling, as the washer in the conventional toggle fastener will typically be sized to cover a standard hole size, but if the axis of the fastener 102 is offset from the center of the hole, the washer is typically too small to cover the entire hole. This problem can arise both through incorrect initial installation, or vibration, or because the toggle bolt is bumped or wiggled, as such mechanical impact can cause the toggle bolt 100 to change position so that the washer is no longer centered on the hole. It is to be appreciated that in construction projects such impacts can occur easily though being bumped with ladders or scaffolding, or other ways.
An example of a device which avoids some of the problems of previous designs is U.S. Pat. No. 4,286,497 to Shamar which discloses a toggle fastener with a plastic ratchet assembly for quickly tightening the toggle and washer against a panel. In the Shamar device, the ratchet assembly consists of two plastic strips attached to the spring-loaded toggle. The strips pass through slots in a plastic washer and include ratchet ridges. The slots in the plastic washer are designed to allow the washer to slide over the strips in the direction of the toggle. To install the Shamar device, the toggle is compressed and inserted into a blind hole. The strips are inserted into the washer and the ends are pulled apart thereby sliding the washer toward the panel and toggle, and securing the fastener to the panel. A means to hang a drop ceiling, such as a bolt, may then be threaded through the center of the plastic washer.
While the Shamar device does decrease the time and effort necessary to tighten a fastener, the design does not meet building and fire codes which prohibit the use of plastic fasteners. Moreover, the amount by which the Shamar device may be tightened is limited by the amount of tension that the installer can generate in the strips and by the amount of tension that the strips may withstand. Also, the Shamar device as well as the prior art device of FIG. 1 do not provide for any self-centering or resiliency once tightened. Any substantial movement of the above described fasteners would cause permanent loss of rigidity and would likely damage either the fastener, the panel, or both, and/or create a passage for fire.
Another example of a prior device is U.S. Pat. No. 4,600,344 to Sutenbach which discloses a push-on plastic wing-nut fastener. This device also decreases the assembly and installation time as compared to conventional toggle fasteners, however as above, building and fire codes would likely not permit its use in general construction and its rigidity and resiliency is limited.
What is desired therefor is a method of mounting a grid for an acoustical ceiling to an existing ceiling which requires a minimum amount of assembly and installation time, which provides a nearly fool-proof fire stop to insure compliance with applicable building and fire codes, and which is rigid once installed yet allows for some resilient deflection that does not cause the firestop washer to be displaced so that the ceiling hole leaves an open passageway for fire.